If the YouTuber can try to gamble on the site he promoted, that can give the site more viewers or visitors. Still, the casino needs to warn the YouTuber or their viewers that playing gambling will be their responsibility and never use big money to gamble.
That will be a good suggestion to every people who watch the advertisement, and the viewers will see that the casino gives a warning before they gamble.
That kind of sponsor is one way to promote their platform so that the casino can grow day by day.
So if you are watching the ads on Youtube coincidentally, you can just skip the ads and watch the other ads, which will not make you curious about the gambling games.
But unfortunately, many people do not know about that, and they visit that gambling site and playing for some rounds using the free money or welcome bonus from the site.
The sponsorship will benefit both Youtube and the gambling site, and people will need to be wise if they watch the ads.